How to tell my boyfriend he can be too much at work?

My boyfriend and I work together in corporate. We’ve been together almost a year and both transitioned into this job together. I feel the need to be more professional working for corporate.

I feel like he doesn’t realize he’s showing too much affection at work or he gets distracted by me too easily.

He keeps wanting us to go on smoke breaks together and says lovey dovey things in a whisper to me. I loved it at first. But this isn’t the environment to be doing so much of that. He wanted to go on a smoke break when I was dealing with something. He could tell I felt a little uncomfortable and I mentioned “did you forget we’re at work babe? Remember we can’t go on smoke breaks too much together” our boss has mentioned that to him before, I went anyway with him though but I could tell he had a switch in his mood after I said that.

How do I tell him this without him getting offended?
he’s acting weird with me already.

Updates
1 y
He broke up with me for the 3rd time these last 3 months. He kept breaking up with me over small things that shouldn’t even be a threat to a relationship, when he doesn’t actually want to break up. He’ll say we’re breaking up and I chase him to convince him to stay last 2 times. This time I’m not having it, how can someone say they love you and break up when things get a little difficult after a simple argument? Not playing into his power moves and I put my foot down
How to tell my boyfriend he can be too much at work?
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